Tuesday, July 5, 2011

Color calibration FTW

So today's blog topic is a very important one covering one of the critical things you need to understand when setting up your own digital darkroom... Color Calibration.

So what is it?

Well here is the deal... take a picture, and then send it to a decent photo lab to make a print of it... then open that same picture on your computer in the windows photo viewer... then compare... what do you see?

The photos look different. The colors are not quite the same. The tone is just totally off, and it may be brighter or darker then you saw on the screen.

So what is the problem here?

Well there are several.... First the problem lies with your output.. You see your monitor/computer just isn't out of the box going to know how to display the colors as they are supposed to look (As compared to the standard).

(Note: your image file is made up of pixels.. each of which has four values.. Red, Green, Blue, and Luminosity. RGB tell the computer what the color is, and luminosity gives the brightness...)

So for a particular RGB (Red, Green, Blue) value the actual color displayed is not going to match the standard as to what that color is supposed to look like. There will be error due to the design of the screen, and due to tolerances within that particular one (because after all unless you buy a very expensive monitor designed for graphic work they just kinda slap em together). Also most monitors are setup (With their on board controls) to be optimal for business or video games. Typically they have cold color tones and lots of contrast. This pumps up the brightness and makes the black deep.. but it kills all the highlight details and makes skin look colorless. The resultant display may be "pleasing" to your eyes and good for viewing a PowerPoint presentation, playing a game, or watching YouTube videos... but the images won't be faithful to their source data.

Another problem is with the software you use to display the photo. Every image has a color space associated with it. The color space defines what a particular RGB value is supposed to look like. There are several, but the one most often used by digital photographers is sRGB. Only software that has built in color management can read the image data and interpret it against the color space and then display the colors correctly. Otherwise the colors will (Again) be off.

The only software that I know of that has built in color management is Adobe Photoshop, and Lightroom. Other adobe products probably have it.. as well as other professional (or serious amateur) level software. However your standard windows photo viewer will not, and your Internet Explorer (or Firefox) will not either.

Obviously.. if you fall into one or both of the two issues above you won't be able to process your images properly for print. Without a true display of how the image will look on paper you can't possibly adjust the exposure, color saturation, and etc. Anything you do will be a shot in the dark. So if you are in this situation it is imperative you take action to establish a better "digital darkroom" for your work.

Calibrate your Monitor
FIRST... you need to calibrate your monitor/computer. This is easier then it sounds.. but does require a small investment in a calibration tool. DO NOT go by any of those tutorials that tell you how to do it with your eye... its not worth the time.. The tool will be some software, and then a colorometer which attaches to your monitor screen or hangs in front of it. The software will display RGB values and grey scale values and the meter will read them. The software will compare the measured output with what it is supposed to be.. and then generate a color profile for your computer/monitor. The profile tells your video card how to adjust the display output so that the RGB values more closely match the standard.

One of the best bang/buck monitor calibration tools is the Spyder tool from ColorVision. I use the Spyder2, and I believe they have the 3rd version out now. There are other tools which some say are "better" but they cost quite a bit more.

Use the right software..
Now.. the second problem.. software. Obviously this is simple.. you need to use software that supports color management. Adobe products do so that is a start. I am a big advocate of photographers using Lightroom (or Photoshop) so if you are doing that then you are already all set. If you are not using Adobe then investigate if your current chosen software does support color space.. if it does not then it is time to switch.

Just remember.. that even if you calibrate your monitor you MUST be using a color managed photo viewer see the image correctly. One without the other won't cut it. Yes.. you may be a little better off with a calibrated monitor alone... but not good enough for editing (maybe display.. not editing for print).

One additional thing to keep in mind... yes printers get calibrated too. :) Actually the combination of Printer, chemicals or ink, and paper get calibrated and output adjusted so that the resultant prints meet the standards. A good lab will do that periodically, and it MUST be done for every combination of ink and paper used.. Normally a printer comes out of the box with drivers and software calibrated for the OEM paper and ink. So if you buy a canon printer and use canon photo paper with canon ink you are nearly good to go. However if you use Costco paper the calibration will not hold. The same is true for labs that use photographic paper printers.

If you use a good lab like Mpix, or even Costco, they normally will calibrate their systems as part of regular maintenance. Your local drug store probably won't.

One final bit of info: most good labs will provide you a color profile for their printers. These are similar to the profile you make for your monitor except it is for the printer. What can you do with it? Well if you are using Photoshop you can install that profile and use it for soft proofing. Even if you calibrate the printer there will be some limitations. Some colors will just look a little different because of the nature of the paper. One example I know of is that Kodak Endura paper (as good as it is..) will display bright reds more subdued. What the soft proofing will show you is how the image on your screen will look once printed on the printer.

So when you have your monitor calibrated.. your color managed Photoshop.. AND a profile for the output printer.. you will have a true digital darkroom where you can preview exactly what you will get as physical output.

Is that the only calibration with digital photography? No of course not. Cameras, for one get calibrated for better raw file processing. Lens/body combinations can get focus calibrations done so that the auto focus is more spot on. Each improves your work just a bit more.

My above explanation is pretty simplified and thus I omitted a lot of the technical jargon and theory (etc).. there are plenty of resources out there on the net if you want to know more on these topics.. however the above is the practical info you need.

1 comment:

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